1. Field of the Invention
The present invention relates to a process for preparing a positive resist composition including a quinone diazide compound.
2. Description of the Related Art
A positive resist composition comprising an alkali-soluble resin and a quinone diazide compound is used in the production of integrated circuits by photographic etching.
Hitherto, a positive resist composition has been prepared by mixing an isolated quinone diazide sulfonic ester with an alkali-soluble resin, a resist solution and so on. Namely, a quinone diazide sulfonyl halogenide undergoes a condensation reaction with a phenol compound in the presence of an alkali in a polar organic solvent such as dioxane, methyl ethyl ketone or mixtures thereof. After the condensation reaction, additional steps including precipitation with, for example, water or methanol, filtering, drying and isolation of the quinone diazide sulfonic ester are required to remove the polar organic solvent used in the condensation reaction step and impurities such as salt by-produced in the condensation reaction and water.
In this process, a processing time is greatly prolonged, because the process includes the steps with inefficient operability and productivity such as filtration and drying.
Another process includes adding a resist solvent to the resulting solution from the condensation reaction without precipitation, filtering or drying, then removing the impurities from the mixture and recovering a solution of the quinone diazide sulfonyl ester in the resist solvent. However, since the solubility of the quinone diazide sulfonyl ester in the resist solvent is low, the quinone diazide sulfonyl ester is easily precipitated in the resist solvent.
Therefore, it is difficult to employ these processes industrially.